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US 9,070,399 B2Granted
Polishing liquid composition for magnetic-disk substrate
AssigneeKao Corporation
InventorsTakeshi Hamaguchi, Haruhiko Doi
Life of this patent
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Abstract
There is provided a polishing composition for a magnetic disk substrate that can reduce scratches, nanoprotrusion defects, and substrate surface waviness after polishing. The polishing composition for a magnetic disk substrate that contains: a copolymer that has a constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. and a constituent unit having a sulfonic acid group, and has a saturated hydrocarbon chain as the main chain thereof, or a salt of the copolymer; an abrasive; and water.
Claims9
A polishing composition for a magnetic disk substrate, comprising:
- a copolymer that has a hydrophobic constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. and a constituent unit having a sulfonic acid group, and has a saturated hydrocarbon chain as the main chain thereof, or a salt of the copolymer;
- an abrasive;
- and water;
- wherein the total proportion of the hydrophobic constituent unit and the constituent unit having a sulfonic acid group relative to all the constituent units constituting the polymer is 90 to 100 mol %,
- wherein the hydrophobic constituent unit is derived from styrene, and the constituent unit having a sulfonic acid group is derived from styrenesulfonic acid or its salt, and
- wherein the molar ratio of the constituent unit derived from a monomer having a solubility of 2 or less 100 g of water at 20° C. to the constituent unit having a sulfonic acid group in all the constituent units constituting the copolymer is 10/90 to 60/40.
3 more elements
Dependencies are inferred from the claim text.